what does pink mean when I try to append a material?
Pink means that the image texture used is not available.
Either it does not exist in the hard drive, or it is in a folder that is not accessible, or has been renamed, or it could mean that the image cannot be mapped the way it is set up on the material.
By default, Blender does not store images used as part of the file, it just uses a reference to the path in the computer where such images are saved.
If you want to save images as part of the .blend file, you need to pack them.